We mix our own feed, buying fertrells mineral mix and adding it to some grains at a certain rate. That said, a lot of micronutrients/probiotics are moot in the free range world.
If your not concerned with large scale production efficiency, we've had good luck doing it much simpler
Compost/free- range - micro nutrients
Calcium - they need supplement, eggshells suck it out of them. Crush their eggshells and feed them back; or buy oystershell supplement and offer it ad lib
Protein/fats -
chickens are omnivores. They'll eat insects all summer, but if you have a time without insects (winter), you'll want to get them some of these. Fishmeal, cooking fats from your kitchen,
dairy products
Carbs - Corn, oats, soy etc. Pretty much everything but corn also has a protein component. Corn is convenient and makes a good treat. If you free-range I would scatter on a hard surface, not ad lib
Don't forget, if there's no small gravel around , buy some grit (its cheap) and offer it ad lib as well.
Ratios?
Calcium and grit year round ad lib
Winter: Roughly 2/3 corn, 1/3 soy/oats/barley, mineral mix if you want, animal protein if you have it
Summer: throw some corn on the ground unless the
chickens are outgrazing the pasture. Animal protein if you have it (they'll polish off an acre of insects long before an acre of grass)
btw these are all maintainer ratios. The younger they are, the higher protein they need, and smaller grit. I always start chicks with unmedicated chick starter and switch them to feed
Also, con